Pyridoxal-5′-phosphate (PLP), an end product of vitamin B6 metabolism, plays a vital role in mammalian health. Vitamin B6 typically refers to pyridoxine, which is chemically known as 2-methyl-3-hydroxy-4,5-di(hydroxymethyl)pyridine and is represented by formula I:
Yet two additional compounds, pyridoxal of formula II
and pyridoxamine of formula III
are also referred to as vitamin B6. All three compounds serve as precursors to pyridoxal-5′-phosphate (PLP), which is chemically known as 3-hydroxy-2-methyl-5-[(phosphonooxy) methyl]-4-pyridine-carboxaldehyde and is represented by formula IV:

PLP is the biologically active form of vitamin B6 inside cells and in blood plasma. Mammals cannot synthesize PLP de novo and must rely on dietary sources of the precursors pyridoxine, pyridoxal, and pyridoxamine, which are metabolized to PLP. For instance, mammals produce PLP by phosphorylating pyridoxine by action of pyridoxal kinase and then oxidizing the phosphorylated product.
PLP is a regulator of biological processes and a cofactor in more than one hundred enzymatic reactions. It has been shown to be an antagonist of a purinergic receptor, thereby affecting ATP binding; it has been implicated in modulation of platelet aggregation; it is an inhibitor of certain phosphatase enzymes; and it has been implicated in the control of gene transcription. In previous patents (U.S. Pat. No. 6,051,587 and U.S. Pat. No. 6,043,259) the role of pyridoxal-5′-phosphate, and its precursors pyridoxal and pyridoxine (vitamin B6), in mediating cardiovascular health and in treating cardiovascular related diseases is disclosed. PLP is also a coenzyme in certain enzyme-catalyzed processes, for example, in glycogenolysis at the glycogen phosphorylase level, in the malate asparatate shuttle involving glycolysis and glycogenolysis at the transamination level, and in homocysteine metabolism.
There is a need to identify and administer drugs that can mimic one or more of the known biological actions of vitamin B-6 congeners but that are more potent than the vitamin B-6 congeners in their specific mode of action.